Mercury switch tester



Feb. 1950 c. F. BROWN MERCURY SWITCH TESTER 2 Shets-Sheet 1 Filed July 8, 1947 await/141M CALVIN F BROWN Feb. 21, 1950 c. F. BROWN 5 MERCURY SWITCH TESTER Filed July 8, 1947 2 Sheets-Sheet 2 FIG. 3 23 I 28 I 27 35 24 I8 29 4 36 39 43 4 Q I l7 l3 jwvQ/ww'i CALVIN F. BROWN tamed a desired speed, when that switches may "tion, specifications and drawings in which:

' Fig. 1 is an enlarged vertical sectional detailed view or a switch testing device embodying the Patented Feb. 21, 1950 UNITED STATES PATENT MERCURY TESTER A v v Calvin F. Brown,

Silver Spring, Md., assignor to the United States of America as represented by the Secretary of the Navy Application July 8, 1947, Serial No. 759,630

Claims. (Cl. 175183) This invention relates to a method of testing mercury switches and an appliance therefor.

The appliance includes a power operated rotor to simulate a spinning projectile in flight, whereby the mercury is displaced from a contact chamber of theclosed switch through a permeable partition to a separate sump to open the switch. In switches of the type adapted to be tested by the mercury switch tester of the invention, a globule of mercury iscontained in an interior contact chamber and acts as a fluent conductor between two spaced contacts to maintain the switch in normally closed condition. The switch to be tested forms no part of this invention.

The rotor, or rotary carrier, is provided with means for initially holding the closed switch axially therein until said rotary carrier has atthe switch is forced centrifugally to an ofi-center or eccentric position, and the mercury drained by centrifugal force from the contact chamber to the sump.

The method of testing consists in timing opening of the switch which resutls from the passage of the mercury from the contact chamber through a permeable partition into the sump, so be determined to operate within'a known time under a standard centrifugal i'forc'e. I

-"In order better to describe the present invenreference is made to the accompanying invention showing a mercury switch centered in an initial position on the axis of rotation of the rotor, or rotary carrier, and clamped by a depressed abutment under pressure of an axially aligned hand tool;

Fig. 2 is an exterior elevational view of the switch tester on a reduced scale;

Fig. 3 is a fragmentary sectional view similar to Fig. 1 showing the switch'unit to be tested in testing position. I

Fig. 4 is a schematic plan view showing an electrical circuit employed with the testing appliance of the invention.

Referring to the drawings it is seen that the rotor, as a unit, is mounted upon an upright spindle or rotary shaft I0 which is driven from a suitable source, and carries the mercury switch to be tested as shown at II. The switch is clamped or clasped in a channel or groove 39 in a circular head I2 of the rotary unit, the said channel being insulated as at I3; and the head in its upper face being recessed, to receive and contain a fixed, concentric conductor ring I4 which is insulated from the head by an insulating assembly I6. The vertical position of the axis shaft I0 assures a centrifugal force unmixed with gravitational or other forces. The rate of rotation of the shaft governs the centrifugal force,

and this rate of rotation may be obtained from a suitable tachometer (not shown). attached to the shaft. 7 v I A holder for the switch includes aradially are ranged, spring biased plunger orclamp pin I! mounted for sliding movement in a sleeve 31 carried in the circular head I2." Thus the switch is held firmly between the end of the pin .I land a movable jaw or abutment I8.

The abutment I8 isv fashioned as an integral jaw projecting downwardly from an upright tubular depressible sleeve I9 which terminates at its upper end in a head 20 having an exterior central cavity or seat 2| for a portable hand tool 22. The sleeve I9 is reciprocable in an open-end upright cylindrical guide 23, here shown as hinged at 24 on the top of the circular head I2. A spring 26, anchored at its ends to the depressible sleeve and the stationary guide, respectively, tends to lift or retract the jaw I8 from the position in which it engages one end of the switch I I. The longitudinal movement of this tubularplunger is guided by co-action of a guide lug or screw 21 on the plunger with a complementary groove 28 of the hinged holder. e

For holding down the switch during the time test, a conventional latch assembly, shown generally at '29, may be carried by the shoulder 30 of the guide 23 and adapted to engage a latch stop 3| in the head I2. I I v A spring biased detent 35 carried by the head I2 is adapted to engage an indentation 36 in-pin I1 to restrain the pin in its retracted position while the switch is inserted in the head I2 and the abutment I8 lowered into place. In carrying out the test, the guide sleeve 23 is first swung on its hinge 24, and the switch II is inserted by hand in the recessed head I2 with its base end against the spring-thrust pin H. The guide sleeve 23 is then restored to upright position, the hand tool 22 is applied to the cavity 2| and then by pressure on the tool the tubular plunger is depressed so that the abutment I8 engases the other end of the switch. The switch is now rigidly held axially within the head l2 as in Fig. 1.

The rotary shaft or Spindle is now driven to spin the head I2 and its contained switch. Upon attainment of the desired rotational velocity, the

"common ground the unit to permit displacement of said pressure on the hand tool 22 is released, the abutment l8 automatically lifted from engagement with the switch, and the spring biased pin i1 and centrifugal force projects the switch to the eccentric position of Fig. 3 and in contact with the ring l4. Due to the continued rotation of the head 12 with the switch in eccentric position, centrifugal force of the spinning head causes the flow of themercury that opens the switch. The time required for the switch contacts to open may be determined by a s table electric time clock 4'2. One terminal of the clock is adapted -;to ,be connected to a suitable source of operating voltage (not shown) and connected to the head I! "of the testing unit through a suitable sliding contact 43. Another sliding contact 44 carried by tacts the conductor ring M, to complete a cirthe other terminal isshownthe holder I 32 con-.

holder including means so insulated as to form branches of an electrical circuit to be bridged by the unit, and an electrically operated time clock in electrical circuit with said unit and said branches and operable for indicating the time required to cause the unit to function under centrifugal force.

3. An appliance for determining the time necessary to break the circuit through a mercury switch under test in response to a predetermined centrifugal force comprising a rotor mounted for rotation about a vertical axis, a work holder mounted on said rotor for mounting a mercury switch in a plane normal to said axis, said work for initially retaining said switch on'theaxis, a spring pressed plunger for urgingthe switchaway from the axis along said plane, a ring for retaining the switch at a fixed cuit through the switch contacts simultaneously" with the displacement forcetogether with the 'action of the spring biased plunger ll. This 'circui-t'may be tracedas follows: 'from the s'li'ding'contact-M, through the head 12, the sleeve -31, the plunger IT, to one 'switchtermin'al; fromthe other switcht'erminal to the conductor *ring H, sliding contact "M, through the time clock and voltage supply source hack to sliding'-contact Obviously the'circuit may be modified for the "potential source and switch terminal.

Aite'r'the test,'-th'e-switch H is turned end-forend and'replaced ineccentric-position; the rotary of switch II by centrifugal by providing, for example, a I

carrier is then revolvedan'd bycentrifugalforce T the mercury is returned irom'the sump to the a conducting chamber, to-close the switch and-restore it toits initialnormal-condition.

"I claim:

'l. A centrifugal testing appliance comprising a rotor, a work holder mounted thereon, said holder including "a spring*pressed-plunger and a movableabutm'erit'coacting therewithfo'r initially holding on the rotor axis a unit to be tested, means for moving holder including *a spring pressed plunger-and a a movable abutment coacting therewith f-or holding on the rotor axis aunit to be testedgmeans to'r movin'g the abutmentout of engagement with unit from the axis, a stop positioned to c'oa ct with. the plunger for retainin'g the unitin displaced off axis "position whereby 'the nnit is subjected to centrifugaI- forca 'sa-id plunger' and saidstop being the abutment out of en'gagement with said u'nitto permit displacement of distance from the axis whereby a predetermined centrifugal force acts thereon, said retaining means including an electrical contact element and a "spring ressed plunger, mearis insul'atin'g "the contact element from I the nolder and plunger, electrical circuit means for supplyingcurrent to the element and plunger respectively and through said switeh and timing meansi-n said 'circuit'with the contact and operable to indicate the time necessary for the switch to breakthecircuit-under aknow-n centrifugal-fierce.

-4.--A centrifugalswitchtesting appliance comprising means for rotating at '-a rsubstantially fixed rate :a switch :to 'be -tested, :ispring pressed plunger :and spring :pressed Labutment --.elements for retaining saiduswitehon theaxisof rotation. means for-releasingthe-abutment-for spring actuated movement outzof retaining, position whereby the spring action of thezplunger 5 may force :the unit away from isaid aXis, means forpassing an electrical current :through the unit-in displaced off-axis position, and means for measuring "the time period of-flow "oi-current.

5. A centrifugal testing appliance -for subjecting a unit to be tested to amredetermined centrifugal force, comprising a rotor adapted for rotation at ameasured rate, timing rneanslconnested in series with :a unit -to be tested and is source of electric current, means-for initialll holding on the :axis of 'saidzrctor'the unitetoibe tested, and means for displacing the unitarpredetermined distance irom 'th'e axis,-upon'- the sattainment of the desired rotational velocity bythe rotor, whereby the unit is subjected tosaidpredetermined centrifugaliorca-said timing means indicating theti-m'e required to cause the -unitto function in this latter position.

GALVINF. BROWN.

5 'CIT'ED The following references are of record inthe file oi this'pa tentt UNITED"STATES PATENTS "Name Date Number Smith in ll/lay 12. 1931 

